Modify optimize-testing instructions
Mention -flto and whole-program optimization as this is the most
important aspect.
Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/docs/architecture/psa-shared-memory.md b/docs/architecture/psa-shared-memory.md
index 279e865..081095f 100644
--- a/docs/architecture/psa-shared-memory.md
+++ b/docs/architecture/psa-shared-memory.md
@@ -239,7 +239,8 @@
It is unclear whether the compiler will attempt to optimize away copying operations.
Once the copying code is implemented, it should be evaluated to see whether compiler optimization is a problem. Specifically, for the major compilers and platforms supported by Mbed TLS:
-* Build Mbed TLS with the compiler set to a high level of optimization (e.g. `-O2` for `gcc`).
+* Write a small program that uses a PSA function which copies inputs or outputs.
+* Build the program with link-time optimization / full-program optimization enabled (e.g. `-flto` with `gcc`).
* Inspect the generated code with `objdump` or a similar tool to see if copying operations are preserved.
If copying behaviour is preserved by all major compilers and platforms then assume that compiler optimization is not a problem.